1. Field of the Invention
The present disclosure relates generally to polymer photonics, and more particularly, to an additive method for manufacturing polymer optical waveguides and devices.
2. Background of the Invention
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A conventional method for polymer optical waveguide fabrication, illustrated in FIGS. 1A to 1C, uses exposure and other development processes to define the desired pattern into a resist coated on top of a substrate 11 with deposited first cladding 12 and core layer 13 materials, and further transferring the resist pattern to the core polymer via plasma etching. Upon patterning to form the waveguide cores 14, a second cladding layer 15 is deposited on top of the waveguide cores 14. This method, although straightforward, is not a cost-effective production method due to complicated fabrication processes and low throughput. The waveguides 14 also suffer from poor sidewall quality, thus increasing the waveguide loss.
Another conventional method for polymer optical waveguide fabrication is to directly expose the waveguide pattern in a photo-curable polymer core material using photolithography, and removing the unexposed material.
Both of the above conventional methods produce waveguides with relatively rough sidewalls. Additionally, since a lot of material is wasted during fabrication, an additional expense is added to the production of the waveguides.
A different method for forming optical waveguides for printed circuit boards was disclosed by Kim et al. (U.S. Pat. No. 8,265,445 B2). First, a first cladding layer is disposed on the base board. Next, an insulation layer is disposed on top of the first cladding layer. A through hole is formed in the insulation layer in order to accommodate waveguide cores. Next, a core material is filled into the hole. In order to planarize the surface, a thin transparent film is laid on top. After curing the core layer, the transparent film is removed. Although the method promises cost reduction compared to the conventional process via filling a limited quantity of core material in the through hole patterned in an insulating material, the process of light exposure and development of the core material to form waveguide channels does not eliminate unnecessary wastage of core material.
Alternatively, an all additive process can eliminate the use of chemicals for removal of materials, thus providing facile routes for developing polymer optical waveguide systems with low cost and without the harmful effects of etching.
Accordingly, several methods have been proposed for developing polymer optical waveguides incorporating fully additive techniques.
Ink-jet printing of core material directly on top of a polymer cladding material has been investigated. However, the waveguide structures have very poor aspect ratios and cannot be made thick enough for practical applications.
Molding/imprinting methods can effectively overcome some of these shortcomings by providing patterning capabilities at both micro- and nano-scales. Although extensive research has been conducted on using various kinds of molds to pattern the core trench for optical waveguides and devices, the predominant core forming technique has been via spin coating, which is not a viable manufacturing alternative, due to the material waste generated during spin coating.